Installed air ducts are typically assembled from tube sections that are coupled with a variety of connectors, tees and vents. Modification of existing systems requires severing the ducting and installing a new connector such as a tee to divert flow in a new direction. Additional vents or control valves can be installed in the branch circuit to regulate the flow. The connectors are expensive and add weight to the system. In addition, installation of a conventional connector permanently alters the ductwork and even if the branch circuit were removed, a replacement coupling would have to be reinstalled. Alterations of this sort sever the continuity of the duct and add potential leaks to the system.
When a branch duct is added to a ducting system, a method is required to control the airflow through that branch. Commonly, this is done by inserting a perforated metal or plastic “restrictor plate” into the duct joint. Sometimes, restrictor plates are installed on branch ducts such that the airflow through the duct tends to pull the aperture away from the branch. An adhesive or bonding agent is generally used to ensure that restrictor plates do not become detached or misaligned within the duct. Adhered restrictor plates are also less susceptible to vibration and will retain more strength following damage due to corrosion. Further, adhered restrictor plates cannot be misplaced when ducting is disassembled for maintenance.
Unfortunately, using bonding agents can present problems. Bonding agents require time to cure, consequently manufacturing planners typically desire all restrictor plates to be bonded to the ducts at the assembly level to reduce delays in a factory. This practice can be impractical however; if assembly drawings are released before a final determination of the flow balance for an application is available. Furthermore, late customer changes and problems discovered during air flow balance tests can also lead to restrictor plate changes, sometimes moments before delivery. Making these changes on the assembly level would require significant changes to assembly and installation drawings at a considerable cost.
Accordingly there exists a need to enable late-stage modification and installation of airflow restrictor plates to accommodate engineering processes, preventing accidental changes to restrictor plates during modification to ensure safety and performance, while avoiding the expense and delays of bonding to accommodate manufacturing processes.
This concept allows a conventional, easy-to-analyze, restrictor that can be quickly inspected and changed without disassembling or severing ducts into pieces. The design attempts to dramatically reduce the time to install restrictor plates, the time to inspect and verify restrictor installations, and the time to change restrictor plate installations after assembly.